The field of this invention relates generally to linear motor and rotational motor structures; more specifically, this invention relates to linear actuators utilized in the isolation of platforms in inertial stabilization systems. Systems commonly utilized for stablization include devices directed primarily to rotational motor systems as well as single axis actuator systems which utilize very narrow gap magnetic elements. This results in a cumbersome structure which requires an individual motor for each axis of rotation, or it requires a plurality of individual linear actuators, one for each translational axis of motion desired, or multiples thereof if rotational motion is desired.
A significant improvement over the above systems is disclosed in U.S. Pat. No. 4,443,743, entitled "Two Axis Actuator", and issued to Edward L. Forys, et al., and assigned to the assignee of the instant application. This device provides force along two translational axes through the interaction of multiple windings on a single platen which interacts with the field poles of a magnetic member. Each platen is meticulously wound such that the current flowing in one direction is maximally exposed to the magnetic field lines of the magnetic member, but the return path current is bunched in a small area of greater depth for minimal exposure to the magnetic field. The windings on each platen are geometrically complex and are therefore expensive to fabricate.
The asymetric geometry of the coils and their relative movements within the magnetic field as the actuator is operated cause the force produced to become more of a function of the angle of rotation than if the coils were of a simple geometric shape. Special winding procedures are required, along with special potting tools. A high rejection rate results from the complex geometry of the coils. Since the return current in the '743 invention was in the magnetic field, an undesirable counter electromotive force was present, thus causing a significant inefficiency. The weight of the platen coils is also important. For the same electromotive force, the peculiar geometry of the platen coils dictated more windings and therefore a greater weight.
The shape of currently used systems limit the application of such systems to custom gimbals and stabilizers. For space applications, efficiency is of paramount importance. Less efficiency implies more electrical current to do the same job, and therefore less current available elsewhere, or a greater payload required to lift more fuel or solar cells.